The present invention relates to a vehicle-body structure of a vehicle equipped with a front bumper reinforcement or a rear bumper reinforcement which has a closed cross section.
In general, the front bumper reinforcement or the rear bumper reinforcement is comprised of a panel member (bumper beam) having a U-shaped cross section and another panel member (closing plate) formed substantially in a flat-plate shape which are jointly fixed together so as to receive an impact load thereat. An article formed in a hat shape which is disclosed in Japanese Patent Laid-Open Publication No. 2012-110944 has been devised as such a front bumper reinforcement or a rear bumper reinforcement in order to improve a resistant force against the impact load.
That is, as shown in FIG. 10, a bumper reinforcement 89 is formed by a panel member (bumper beam) 86 having a U-shaped cross section and another panel member (closing plate) 87 formed substantially in a flat-plate shape. The panel member 86 includes an upper face portion 81 and a lower face portion 82 which are arranged in parallel to each other with a specified gap therebetween, a vertical wall portion 83 which interconnects respective one-side end portions (i.e., end portions on the side of a vehicle compartment) of the upper face portion 81 and the lower face portion 82, and flange portions 84, 85 which extend vertically outward from respective the other-side end portions (i.e., end portions on the opposite side to the vehicle compartment) of the upper face portion 81 and the lower face portion 82. The panel member 87 is arranged on the opposite side to the vehicle compartment relative to the panel member 86 and joined to the panel member 86 so as to form a closed cross section 88 extending in a vehicle width direction together with the panel member 86. Herein, step portions 90, 91 are respectively formed at the upper face portion 81 and the lower face portion 82 of the above-described panel member 86. That is, the panel member 86 has its crank-shaped step faces formed integrally at its upper-and-lower both faces. Thus, the panel member 86 having the U-shaped cross section which is disclosed in the above-described patent publication includes the step portions 90, 91 formed at its upper-and-lower both face portions 81, 82, so that the resistant force against the impact load can be improved.
In the conventional structure disclosed in the patent document, however, since the cross section shown in FIG. 10 has the same (identical) shape over its whole width in the vehicle width direction, it may be difficult that the bending strength against the impact load can be ensured and also the light weight of the bumper reinforcement can be attained. Further, there may be room for improving the load transmission from the bumper reinforcement to crash cans.